Field devices are used in industries to control or monitor operation of a process such as an oil refinery. A field device, such as a transmitter, is typically part of a process control or monitoring loop and is located in the field to measure and transmit a process variable such as pressure, flow or temperature, for example, to control room equipment. A field device such as a valve controller can also be part of the process control loop and controls position of a valve based upon a control signal received over the process control loop, or generated internally. Other types of controllers control electric motors or solenoids, for example. The control room equipment is also part of the process control loop such that an operator or computer in the control room is capable of monitoring the process based upon process variables received from transmitters in the field and responsively controlling the process by sending control signals to the appropriate control devices. Another field device which may be part of a process control loop is a portable communicator which is capable of monitoring and transmitting process signals on the process control loop. Typically, such devices are used to configure devices which form the process control loop.
With the advent of low-power microprocessors, field devices have undergone significant changes. Years ago, a field device would simply measure a given process variable, such as temperature, and generate an analog indication in the form of a current varying between 4 and 20 (mA) to indicate the measured temperature. Currently, many field devices employ digital communication technology as well as more sophisticated control and communication techniques. Field devices often employ low-power electronics because in many installations they are still required to run on as little as 4 mA. This design requirement prohibits the use of a number of commercially available microprocessor circuits. However, even low-power microprocessors have allowed a vast array of functions for such field devices.
One new function that is enabled by microprocessor-based smart field devices is the generation of diagnostic information. Through adaptations of hardware, software, or both, today's smart field devices are able to assess the condition of process interface elements such as sensors or solenoids, assess their own circuitry, and/or even assess the relative health of the process control loop itself. Rosemount Inc., the Assignee of the present application, has contributed in this area. See, for example, U.S. Pat. Nos. 6,047,220; 5,828,567; 5,665,899; 6,017,143; 6,119,047; 5,956,663; 6,370,448; 6,519,546; 6,594,603; 6,556,145; 6,356,191; 6,601,005; 6,397,114; 6,505,517; 6,701,274; 6,754,601; 6,434,504; 6,472,710; 6,654,697; 6,539,267; 6,611,775; 6,615,149; 6,532,292; and 6,907,383.
The result of these significant developments in the area of diagnostics for microprocessor-based smart field devices is that a wealth of information is now available relative to numerous aspects of field devices in various process installations. However, considering that a given process installation may include tens, or even hundreds of such microprocessor-based field devices, an operator or technician could easily become overwhelmed by the sheer amount of diagnostic data provided during operation.
A method of processing diagnostic data in order to better utilize the finite maintenance resources of a process installation would increase the degree to which process installations could utilize the wealth of diagnostic information available today.